In the prior art, a geared transmission and a continuously variable transmission capable of varying a speed change ratio steplessly are available as a transmission mechanism for transmitting power between rotary members. For example, a belt-type continuously variable transmission and a toroidal-type continuously variable transmission are known as the continuously variable transmission. Specifically, the belt-type continuously variable transmission is a transmission varying a speed change ratio continuously using a pair of drive pulleys and a pair of driven pulleys, and a driving belt applied to those pulleys. The known endless driving belt used in such belt-type continuously variable transmission is prepared by arranging a plurality of plate members called an “element” or a “block” in a circular manner, and fastening the plate members by an annular metal belt called a “ring” or a “hoop”.
When the driving belt thus applied to the drive and driven pulleys is driven by driving the drive pulley, a frictional force acts on a contact portion between the element and the drive pulley, and a compressive force is applied to the elements in the arranging direction thereof, i.e., in the thickness direction thereof according to a torque of the drive pulley. The compressive force applied to the element being contacted with the drive pulley is transmitted to the element being contacted with the driven pulley via the elements situated linearly between the drive and driven pulleys. When the compressive force is transmitted to the element being contacted with the driven pulley, a frictional force is generated at the contact portion between the element and the driven pulley, and a torque to rotate the driven pulley is established according to the transmitted compressive force. The power is thus transmitted between the drive and driven pulley through the driving belt.
Japanese Patent Laid-Open No. 2000-266130 disclose an invention relating to an element peripheral length measuring method and a measuring device for controlling a clearance between the elements of a drive belt easily and accurately. According to the element peripheral length measuring method and the measuring device taught by Japanese Patent Laid-Open No. 2000-266130, a plural number of elements are arranged in a circular arc shape in a recessed part of a guide block, and the elements thus accumulated and arranged are pressed along the circular arc shape by a pusher. A moving quantity at such pressing time is measured by a linear gauge to obtain a peripheral length along the circular arc shape, and a clearance is computed by comparing the peripheral length of the elements with a peripheral length of a ring member which is previously measured.
Meanwhile, Japanese Patent Laid-Open No. 2005-55283 discloses an apparatus for measuring a clearance between elements of a belt for a gearless drive mechanism. The apparatus taught by Japanese Patent Laid-Open No. 2005-55283 comprises: a pair of opening and closing arms freely opening and closing in a circumferential direction of the belt; a pair of gripping members for sandwiching body parts of the elements from both sides of width directions; and a measuring means for measuring the amount of a clearance between the opening and closing arms on the basis of the amount of operation of a drive source for opening the opening and closing arms. According to the teachings of Japanese Patent Laid-Open No. 2005-55283, the opening and closing arms are opened in the circumferential direction of the belt while gripping the body parts of the elements by the gripping member, and the amount of a clearance between the elements is determined on the basis of a measurement value of amount of opening by the measuring means at the time.
In addition to above, Japanese Patent Laid-Open No. 2005-315288 discloses an inspection device for a continuously variable transmission belt comprising: a large number of consecutively attached metal elements punched and processed into a specified shape; and a metal stepless belt for supporting the metal elements. According to the teachings of Japanese Patent Laid-Open No. 2005-315288, a clearance between the metal elements is quantitatively inspected directly using a wedge-shaped inspection jig.
Further, Japanese Utility Model 59-183557 discloses a driving belt for a continuously variable transmission, comprising: a carrier (i.e., a belt) of an endless metal belt; and a plurality of V-blocks (i.e., elements). Each of the elements comprises a body portion and a carrier groove, and those elements are attached to the belt in a movable manner in a length direction of the belt. According to the teachings of Japanese Utility Model 59-183557, clearances between the adjoining elements are adjusted by an adjustment V-block (i.e., element) having a different thickness to adjust the clearances between the adjoining elements at the end of assembling.
In order to optimize an endplay of a driving belt, the endplay of the driving belt has to be maintained within a desired range by measuring a clearance between the adjoining elements, in other words, by measuring a range of movement of the elements fastened by the ring in the length direction of the belt as the endplay of the driving belt, using the device taught by Japanese Patent Laid-Open No. 2000-266130, Japanese Patent Laid-Open No. 2005-55283 or Japanese Patent Laid-Open No. 2005-315288, and by selecting a suitable adjustment element such as the element for adjusting a clearance between the element taught by Japanese Utility Model 59-183557 in accordance with the measurement result.
However, according to the teachings of Japanese Patent Laid-Open No. 2000-266130, Japanese Patent Laid-Open No. 2005-55283 and Japanese Patent Laid-Open No. 2005-315288, a dedicated measuring or inspecting instrument or tool is required to measure the endplay of the driving belt. Therefore, the cost of measuring the endplay of the driving belt has to be increased to introduce such an instrument. In addition, all of the elements have to be juxtaposed or fastened by the ring to measure the endplay. Therefore, a number of processes has to be increased to arrange the elements and to fasten the elements. As a result, productivity of the driving belt has to be degraded.